The present invention relates to a sprayable foamed composition, and to a method of spraying the composition for covering a material to be protected such as soil, refuse at a disposal site, or other material in a stockpile to form a protective water-resistant layer thereover.
It is common in landfill or dump operations which receive garbage, trash and/or other deposits during the day to provide a covering layer of compacted earth approximately six inches to two feet deep at the end of the day. This earth layer prevents the escape of odors, the blowing of papers and other trash into the adjacent area, the proliferation of pests such as flies, rodents, and birds, and the leaching of toxic or disagreeable components from the dumped material. This cover material provision, often termed xe2x80x9cdaily coverxe2x80x9d, is frequently required by municipal, state, and/or federal regulations which govern such landfill or dump operations.
The task of placing and compacting an earth xe2x80x9cdaily coverxe2x80x9d represents a very significant portion of the landfill operating cost since it employs significant labor and heavy equipment. Such compacted earth cover performs its principle function only for a day or so, that is, each day""s garbage or trash layer is covered at the end of the day and further garbage and trash layers are then piled directly on top of the previous day""s xe2x80x9cdaily coverxe2x80x9d.
Besides the cost of applying the compacted earth cover, it is recognized that multiple earth fill layers used in this way consume a significant volume of the valuable landfill space, which might otherwise be used for disposal. Many areas are rapidly exhausting their available landfill acreage and reducing the consumption rate of the available landfill volume is, accordingly, desirable.
One solution to the provision of such compacted earth cover has been proposed and described in U.S. Pat. Nos. 4,421,788 and 4,519,338 in which means are disclosed for coating the landfill surface with a non-biodegradable plastic foam spray which, in effect, provides the xe2x80x9cdaily coverxe2x80x9d. An alternate solution to this problem is disclosed in U.S. Pat. Nos. 4,909,667 and 4,927,317 wherein a canvas or plastic sheet is daily retracted and extended to protect the working face of the disposal site.
Sprayable compositions have also been proposed for agricultural and erosion control purposes. U.S. Pat. No. 2,802,303 discloses a soil surface treatment utilizing a mixture of a water-soluble cellulose derivative and a finely divided expanding lattice clay for control of natural wind and water erosion of surface soil. The mixture can be applied dry to the soil surface being treated or injected into a stream of water to form a slurry which is sprayed onto the surface.
U.S. Pat. No. 3,763,072 discloses a method of forming a relatively thick semi-impervious crust on soil to inhibit erosion, or in hydroseeding applications to apply seed, fertilizer, herbicide and fibrous mulch. The method includes the step of spraying an aqueous composition onto the soil surface and allowing the composition to cure in the treated soil surface. The aqueous composition contains an aqueous 100% latex emulsion (for binding soil particles together) and sodium silicate (to assist the composition in penetrating into the soil to prevent the formation of a mere surface layer).
U.S. Pat. No. 2,961,799 discloses a sprayable latex composition for treating soil which forms a surface film intimately bonded to the soil particles. The composition includes a water-insoluble counter-penetrant (which inhibits soil penetration by the rubber, and is absorbed preferably by the soil).
Another method for inhibiting erosion and applying seed to a soil surface is disclosed in U.S. Pat. No. 3,600,852, wherein an aqueous slurry consisting mainly of gypsum (as a binder material) and a minor amount of seed is sprayed over a soil surface. The slurry can also contain minor amounts of fertilizer, high bulking water-absorbing filler materials such as cellulosic fibers to facilitate germination, and a set retarder to lengthen the setting time. Foaming agents may also be used.
Other sprayable or extrudable agricultural mulches are disclosed in U.S. Pat. Nos. 3,812,615 and 4,297,810.
Other soil sealing methods which require the composition to be mixed with the top layer of soil to provide a water holding area are disclosed in U.S. Pat. Nos. 3,772,893 and 3,986,365.
The present invention provides a sprayable composition for forming an outdoor cover layer over material to be protected such as, for example, (1) soil, (2) refuse at a disposal site, a sanitary landfill, or hazardous material landfill, (3) a stockpile of material such as grain, ash pits, salt or coal, (4) a temporary cover for remediation sites, or (5) tire piles (which may optionally be covered with a netting material before spraying the composition). When used over soil, the composition can function as a means of providing erosion control and/or a means for distributing seed and fertilizer over the soil. The cover layer so formed remains intact for up to 6 to 12 months and then biodegrades.
The composition includes the following ingredients:
(a) a major amount of a bulking/setting material, such as gypsum or fly ash, for example;
(b) one or more water soluble polymers, such as a cellulosic polymer or a super absorbent polymer, for providing the composition with the desired film forming, gelling and/or adhesive properties; and
(c) a carrier such as water for the bulking/setting material and the polymer such that the composition, after spraying, becomes water-resistant, tough and flexible.
Preferably, the composition also includes a foaming agent to extend the coverage of the composition and enhance the ability of the composition to adhere to sloping and vertical surfaces.
The above composition can also include a clay, such as bentonite, as a non-shrinking inert filler. Furthermore, a fibrous material, such as paper and/or wood fiber, can be added to the composition as a filler and a binder for a matrix formed by the polymer.
A retarder can be included in the above composition to slow the hardening of the bulking/setting agent to allow preparation of larger batches at one time.
Other ingredients can be advantageously added to the composition such as one or more of the following additives: an anti-dusting agent, a dye, and an odor control agent. For planting applications, seed and fertilizer can be added.
The ingredients are combined with the water carrier to form an aqueous slurry which is sprayed or spread by other means over the surface being treated.
The present invention also provides a preferred method of using the above described sprayable composition to form a cover layer over material, the method comprising:
(a) mixing the above ingredients in effective proportions to produce a foamed sprayable slurry;
(b) spraying the foamed slurry at ambient temperature over the material to form a layer of thickness sufficient to cover and protect the top of the material for a predetermined period of time; and
(c) protecting the material by allowing the layer to set up and form a water-resistant, tough and flexible cover layer.
The composition, when sprayed, forms a protective, water-resistant covering layer over material, which has been found to last up to six months to a year, depending upon the ambient weather conditions. The resulting covering layer has the following advantages:
1) easily sprayed at ambient temperature;
2) does not mist in the air when sprayed;
3) tacks down dust or papers that are blown unwantedly by wind;
4) becomes water-resistant when cured and set up after spraying;
5) resists cracking even in hot temperatures including temperatures above 100xc2x0 F.;
6) after setting up, the sprayed layer has decreased surface penetration by precipitation;
7) reduces volatile emissions and controls odor.
In addition, the present invention concerns an apparatus for foaming and spraying the above composition. The apparatus includes means for ensuring the foaming agent is thoroughly blended in the composition before spraying.
Other advantages of the present invention will be apparent to one skilled in the art from reading the following description of the preferred embodiment.